1. Field of the Invention
The present invention relates to a chair.
2. Description of the Related Art
Conventionally, chairs have been proposed for use in offices and the like where when the seated user rests against the back surface portion (i.e., the backrest), the seat portion, which is linked to the seat surface portion, moves. Examples of publications that disclose some conventional technologies include the following.
(1) Official Gazette of Japanese Patent Publication No. 2000-505677
(2) Wilkhahn website online “Modus: Function” on the Internet <http://www.wilkhahn.co.jp/products/working/modus/function.html> (searched Jun. 15, 2006)
FIG. 2 is a drawing showing the configuration of a conventional chair.
In FIG. 2, the 113 is a base portion in a conventional chair and is provided with braces and casters (not shown). It is mounted on a floor surface and is designed to support the weight of the entire chair and that of the user seated in the chair. A seat 114 on which the user takes a seat is rotatably attached to the upper end of the base portion 113 via a joint. A first link 112 that supports a seat back rest 115 is rotatably attached via a joint midway to the base portion 113. Further, the seat surface portion 114 and the first link 112 are linked by a second link 111 rotatably attached to both via joints.
For this reason, when a user seated in the chair leans back against the back surface portion 115, the first link 112 that supports the back surface portion 115 rotates relative to the base portion 113 at the joint axis. Also, the seat surface portion 114 is linked to the first link 112 due to the second link 111 so it moves in conjunction with the first link 112 and rotates relative to the base portion 113 on the axis of the joint.
Nonetheless, with this conventional chair, the seat surface portion 114 does not move as long as force is not applied to the back surface portion 115. Accordingly, the user cannot always take the optimum seated posture.
That is, the chair is such that if the back of the user seated on the seat surface portion 114 is not made to incline more than the angle of inclination relative to the seat surface portion 114 of the back surface portion 115 in the beginning state, the seat surface portion 114 does not move. For this reason, in a case such as when the user seated on the seat surface portion 114 is performing work while facing a desk, if the user is not leaning back against the back surface portion 115, the angle of the seat surface portion 114 does not change. Accordingly, the user is not always able to take the optimum seated posture.